1. Technical Field
This invention relates to control mechanisms and in particular to cam operated control mechanisms wherein a cam follower is caused to snap from one position to another as a result of relative movement between the cam follower and cooperating cam.
2. Background Art
In U.S. Pat. No. 4,130,746 of William J. Linstromberg, which patent is owned by the assignee hereof, a snap action cam for a timer switch is disclosed which is arranged to provide substantially positive throwing of the switch in both directions so as to avoid a dead break condition wherein the switch is maintained in intermediate position between the two operating conditions. The control mechanism is shown for use with an ice maker wherein the switch controls operation of different elements of the refrigeration apparatus and ice maker structure. The snap action cam effectively prevents hangup of the switch which condition had occurred in prior art devices causing undesirable discontinuation of the operation of the ice maker. The switch controls operation of the timer motor which further serves as a means for driving the switch cam itself. The control mechanism utilizes the gradual movement of the cam to effect the desired rapid throwing of the switch to either of its operational conditions.
The present invention is concerned with a control mechanism generally similar to that of the Linstromberg patent but wherein means are provided for assuring continued operation of the control mechanism in the event of a failure of the spring means to move the cam follower from the first position to the second position, such as may result from a breaking of the spring.
While the Linstromberg U.S. Pat. No. 4,130,746 would appear to comprise the closest background art, a number of additional patents are pertinent in this regard. More specifically, Dominick Feroleto in U.S. Pat. No. 3,004,449 shows a cam having a relatively movable portion by means of which the operating surface of the cam is modified during operational use. The invention is intended to provide a variation in the circumferential extent of the cam as a function of the pressure applied by the cam follower.
In U.S. Pat. No. 2,851,593, Stuart Machlin shows a television input tuner wherein a lip and cam cooperate to move the control shaft without utilization of springs or other resilient means. A portion of the cam is discontinuous so as to permit movement of the cam follower therethrough. A portion of the cam follower always remains in contact with the inner cam surface.
Wallace L. Linn et al. in U.S. Pat. No. 3,710,043 show a cam operated switch wherein a deflectable tongue portion is deflected by riding over a ramp to store energy therein, the stored energy being delivered to a switch upon further rotation of the cam beyond the ramp.
Knut J. Magnusson in U.S. Pat. No. 3,236,107 shows a timing mechanism having a plurality of parallel slide cams, one of which includes slots through which a cam follower moves to actuate a switch. Magnusson et al. also disclose a rotary cam having slots through which the cam follower moves.